The adrenal medulla is an endocrine gland which releases several hormones, the most important of which is the catecholamine, epinephrine. These hormones elicit a multitude of responses, including the classic 'fight or flight' response. While the physiological importance of the adrenal medulla is well-documented, several important regulatory mechanisms involved with secretion from this gland are not well-described. This proposal addresses several of these important, yet unanswered questions, involving the cellular and molecular regulation of catecholamine release. The proposed research also investigates the novel hypothesis that the intracellular cytoskeleton is associated with adrenal nicotinic receptors and that this association may be functionally important. The specific aims of the research are 1) to characterize the adrenal chromaffin nicotinic and muscarinic receptors using radiolabeled ligand binding techniques, 2) to investigate the association of adrenal chromaffin nicotinic receptors with the intracellular cytoskeleton and the factors which may affect coupling, 3) to determine the involvement of the intracellular cytoskeleton with the topographical organization and the functional state of the adrenal nicotinic receptor complex, 4) to determine the effects of several different types of microtubule agents on adrenal chromaffin cells, and 5) to investigate the involvement of muscarinic receptors, nicotinic receptors, and possible feedback mechanisms in the regulation of hormone release from adrenal chromaffin cells. The objective is to gain a better understanding of the cellular and molecular mechanisms involved with stimulus-secretion coupling. The research is designed to investigate regulatory mechanisms mediating adrenal catecholamine secretion. Physiologically, the nicotinic receptor is the most important receptor on adrenal cells. When released into the circulation, either during stress or in certain pathological conditions, these catecholamines have very dramatic effects on the cardiovascular and respiratory systems. Because of the physiological importance of this endocrine organ, a more comprehensive understanding of the receptor systems mediating activation of these cells is needed.